Appendix talk:Legendary and Mythical Pokémon/@comment-28922217-20170521135341/@comment-30449951-20170521141151

The creation trio represent solids, liquids, and gasses. Dialga, being a steel type, represents a solid, since steel is a solid. Giritina is a ghost type, representing a gas. Though ghosts aren't really gasses, they have similar characteristics, one being that you can put your hand through it. Palkia is a water type because it  represents a liquid.